(a) Field of the Invention
The present invention relates to an improved method for producing a bearing structure. More particularly, it concerns a method by which a bearing layer of lead-tin-copper can be electrolytically overplated with a protective layer of tin-lead alloy while minimizing waste treatment problems associated with conventional techniques for producing such an article.
(b) Description of Prior Art
It is well known in the art to produce a bearing structure or article by electrodepositing a layer of tin-lead-copper alloy on at least part of the surface of a given metallic substrate. Likewise, it is well known in the art to overplate this layer of tin-lead-copper alloy with a covering layer of lead-tin alloy to both enhance the appearance of the bearing structure and to improve its corrosion resistance.
Conventionally, in the manufacture of a bearing structure, lead-tin-copper electrodeposits are obtained by placing a suitable substrate in an electroplating bath which contains lead, tin and copper ions and then passing electric current through the bath. The so-plated substrate is then subjected to an aqueous rinse treatment to remove plating bath drag-out therefrom before it is over-plated with a protective layer of lead-tin alloy. The resultant rinse material (water) is then treated by conventional waste treatment systems such as evaporation to remove the recovery contaminates therefrom.
The evaporation recovery equipment utilized to treat the rinse water is both expensive to build and to operate. Obviously, it would be desirable to have a technique for manufacturing such bearing articles which is free from such pollution problems and does not require the use of such expensive evaporation recovery equipment.
Accordingly, it is the principal object of the present invention to provide a novel electrolytic technique for producing lead-tin-copper bearing structures which are overplated with a protective layer of lead-tin while minimizing the pollution problems associated therewith.